THE SYNTHETIC PYRETHROID ISOMERS .2. BIOLOGICAL-ACTIVITY

Pure optical isomers of phenothrin, permethin and cypermethrin were sy nthesised and tested on a wide spectrum of insects (Blattella germanic a, Leptinotarsa decemlineata, Tribolium confusum, Oncopeltus fasciatus , Musca domestica, Aedes aegypti). Our results suggest that in the str ucturally related series phenothrin, permethrin and cypermethrin the c hemical modifications had only a small influence on intrinsic activity of the compounds at the target site. The activity of piperonylbutoxid e synergised 1Rtrans phenothrin and 1Rcis permethrin (LD(50)=1.2 ng/fl y in both cases) is in a similar range to the most active 1RcisS cyper methrin isomer alone or with PB (LD(50)=0.9 and 0.4 ng/fly, respective ly). Some cypermethrin isomers considered previously to be totally ina ctive show significant activity depending on the tested insect species . The 1RcisR and 1RtransR isomers proved to be as active as the most p otent isomers on mosquito. A similarly unexpected result was that in t he case of mosquito all four trans isomers were significantly more act ive than the corresponding cis isomers.